Vacuum tube



Dec. 10, 1929. E. Y. ROBINSON VACUUM TUBE Filed Sept. 6, 1923 Patented 10,:1929

UNITED STATES PATENT mm:

mmsr mortar: nonmson, or MANCHESTER, ENoLAnn Assmnon TO ASSOCIATE) mnc'rnrcn. mnusrnms LIMITED, a comm or GREAT BRITAIN vacuum moms l I Application filed September 8, 1928, Serialflo. 681,826, and in Great Britain October 16, 1982.

This inventionrelates to the construction of grids for vacuum tubes such as, for instance, thermionic valves.

The object of this invention is to rovide an improved grid which may be subjected to high mechanical stresses, may be operated at a high temperature and which is compact in the inter-electrode space. Grids constructed according to this invention are particularly suitable for use in valve tubes wherein the inter-electrode space is small, such as those described in my prior Patent No. 1,677 ,850 granted July 17, 1928.

According to this invention the grid is constructed of a.number of wires or filaments which may preferably be of refractory material, such as tungsten or molybdenum) which are held taut by springs.

In the improved construction the grid supporting springs are constructed of thin metal strips having all portions thereof extending in a plane substantially at right angles or transverse to the lengths of the grid wires and wherein the spring eifect is obtained-by the resistance of the strips to bending.

When the electrodes are cylindrical the supporting springs may be composed of a spider embodying strips or plates which are mounted radially, and the grid wires are attached to the springs so that they are stretched and held taut in a substantially axial direction. The grid may consist of a continuous filament wound in a zig-zag path over the supporting springs.

Preferably, the tensioning springs are formed of strips cut out of a sheet of material,

,so that they are integral with each other, or

strip tensioning springs may be welded or riveted to each other or to a common metallic support so that they form an integral support.

Referring to the accompanying drawings Fig. 1 illustrates an application of this invention to a three-electrode valve employing cylindrical electrodes, Fig. 2 is an enlarged detail sectional view of the grid tensioning means, and Fig. 3 represents a transverse section through the valve structure taken on the line 33 of Fig. 1, on an enlarged scale. In the valve or tube illustrated the cathode consists of two concentric tungsten tubes and it is heated in the manner described Y in In prior Patent No. 1,705,377 granted Mare 12, 1929. v

The casing of the valve itself forms the anode which is arranged to be water cooled in any suitable manner (not shown). In the valve illustrated ionization is prevented instarting is shown at 4. In order that the valve may function in the manner described in my aforesaid Patent No. 1,677,850, shields 6 and 7 are provided to confine the discharge to the interelectrode space. The shield 6 is mounted on the central stem 14 and shield 7 consists of a flanged tube which is mounted on the stems supporting the inner cathode portion. The grid 8 consistsofa continuous tungsten or molybdenum filament which is wound in zig-zagform and is supported approximately axially. Said grid is supported at one end by the tube 9 which is provided with projections 10, said projections engaging with the loops in the zig-zag formation of the filament. The filament grid is *tensioned at the other end by means of the spring spider 17 which is comprised of plate springs which radiate from its center.

All insulating portion 20 for example of steatite or lavite is attached to the central stem 14 by suitable means for example by riveting over a reduced portion of the central stem 14. This insulating portion .20

I claim:

1-. An electrode structure for a three-electrode vacuum electric tube embodying a cathode, a surrounding anode spaced therefrom, and a tubular grid comprising a plurality of substantially parallel grid wires which are straight throughout their lengths and extend longitudinally of the interspace between the cathode and anode, a central metal supporting member, and a plurality of plate springs radiating from said central supporting member in a plane substantially at right angles to the lengths of the grid wires, each spring having all portions thereof transverse to the grid wires and being connected to not more than two grid wires and acting on such wires to place them in tension and to su port them so t at they will be free for longitu inal movement while preventing lateral displacement thereof in the interspace between the cathode and anode.

2. An electrode structure for a three-electrode vacuum electric tube embodying a cathode, a surroundin anode spaced therefrom,

and a tubular gri comprising a plurality of substantially parallel grid wires which are straight throughout their lengths and extend longitudinally of the interspace between the cathode and anode, a central metal supporting member, and a pluralit of plate springs formed integrally with sai central supporting member and extending therefrom in a plane substantially at right angles to the lengths of the grid wires, each spring having all portions thereof transverse to the grid wires and being connectedto notmore than two grid wires and acting on such wires to place them in tension and to support them so that they will be free for longitudinal movement while preventing lateral displacement thereof in the intcrspace between the cathode and anode.

In testimony whereof, I have hereunto subscribed my name this eighth day of August,

ERNEST YEOMAN ROBINSON. 

